For example, as a technique relating to a device for measuring mechanical quantity, a strain gauge is often used in order to measure the strain or stress of a structure. The strain gauge has a structure in which a wiring pattern on a metal thin film of Cu—Ni alloy or Ni—Cr alloy is covered with a polyimide or epoxy resin film. The strain gauge is used by being bonded to the object to be measured with an adhesive. The strain gauge can calculate a strain quantity based on the resistance change of the metal thin film being strained and deformed.
Further, a semiconductor strain sensor is employed which has a strain detection unit using not the metal thin film but semiconductor piezoresistance formed by doping impurities in a semiconductor such as silicon. The semiconductor strain sensor has a resistance change rate relative to strain, which resistance change is several ten times as large as that of the strain gauge using the metal thin film, and the semiconductor strain sensor is allowed to measure minute strain. The strain gauge having the metal thin film has a small resistance change, so that an obtained electric signal needs to be amplified, and thus another external amplifier is required. The semiconductor strain sensor has a large resistance change, on the other hand, so that an obtained electric signal can be used without an external amplifier, and the semiconductor strain sensor may include a semiconductor strain gauge chip in which an amplifier circuit is integrated. Therefore, the application or convenience in use of the strain sensor is expected to significantly increase.
The semiconductor strain sensor has a semiconductor strain sensor chip obtained by chipping a silicon wafer on which impurities have been doped or wiring has been formed by a conventional semiconductor production technique. The chip (hereinafter referred to as semiconductor strain sensor chip) is incorporated into a device including a plastic resin or the like to measure a mechanical quantity such as manual or mechanical deformation quantity or stress input to a housing. In order to obtain electrical output according to the input in the measurement, it is important to accurately transmit, to the semiconductor strain sensor chip, the deformation quantity or strain quantity of the housing as an object to be measured, and it is also important to modularize the semiconductor strain sensor chip as well as to mount the semiconductor strain sensor to the object to be measured.
A technique relating to such a semiconductor strain sensor chip includes, for example, a technique described in PTL 1. PTL 1 discloses a method for joining a semiconductor strain sensor chip to a base plate and connecting the base plate to an object to be measured through two connection areas on the base plate on both sides of the semiconductor strain sensor chip.